Avoid reimporting lightmap textures every getter call

[gongpha]

• Fixes LightmapGI : Duplicating any LightmapGIData crashes the engine #77777. (I didn't notice that was a fantastic number - -)
• Bugsquad edit: Fixes Moving nodes around the tree in a scene with baked lightmap triggers lightmap reimport #83444

Also improves #61861. The _get_light_textures_data function is trying to reimport lightmap textures on every getter call which sounds irritable to me (e.g. when the engine is reading the property via duplicating).

[Calinou]

Tested locally (rebased on top of master 329652b), it works as expected. I no longer get a crash with the MRP.

However, we will need to implement a compatibility handler so that users aren't forced to rebake lightmaps when upgrading. (This can take a long time on complex levels with high quality settings, especially if you have a slow GPU.)

[akien-mga]

This indeed needs some compatibility code added. The old methods should still be registered as compatibility methods for GDExtension, and existing data should ideally be parsed and converted to the new format (which can be done via the _set/_get methods).

[atirut-w]

I don't know what went wrong during the time I last tested this branch, but it no longer works. It crashes with an out of bound error seemingly when there are more than one lightmapped meshes in a scene.

...
ERROR: FATAL: Index p_index = 1 is out of bounds (size() = 1).
   at: CowData<class Ref<class Image> >::get (C:\Users\atiru\Projects\godot\core/templates/cowdata.h:155)

================================================================
CrashHandlerException: Program crashed
Engine version: Godot Engine v4.2.dev.custom_build (865c25adfc9f9842dde9aaf3162f1b768de57c6c)
Dumping the backtrace. Please include this when reporting the bug to the project developer.
[0] CowData<Ref<Image> >::get (C:\Users\atiru\Projects\godot\core\templates\cowdata.h:155)
[1] Vector<Ref<Image> >::operator[] (C:\Users\atiru\Projects\godot\core\templates\vector.h:96)
[2] LightmapGI::bake (C:\Users\atiru\Projects\godot\scene\3d\lightmap_gi.cpp:1088)
[3] LightmapGIEditorPlugin::_bake_select_file (C:\Users\atiru\Projects\godot\editor\plugins\lightmap_gi_editor_plugin.c)
[4] LightmapGIEditorPlugin::_bake (C:\Users\atiru\Projects\godot\editor\plugins\lightmap_gi_editor_plugin.cpp:113)
...

MRP (don't mind the namings, I reused an old MRP): crash.zip

[gongpha]

This crash issue seems not related to this PR. I only refactored the old porting PR (#61861) and removed unnecessary importing operations. You may create a new issue and fill in details about the issue and MRP.

[atirut-w]

This issue does not happen in c5a7462, which is the parent of this PR's branch. That should confirm that this issue is caused by something during all those rebases and forced pushes. The stack trace also points to a file touched by this PR:

[2] LightmapGI::bake (C:\Users\atiru\Projects\godot\scene\3d\lightmap_gi.cpp:1088)

[AThousandShips]

See above

Needs to be verified but should fix the issue

[atirut-w]

@AThousandShips I tried out your fix on my end and it still crashes with the exact same log, but seems to have progressed a little more. Before, it only said "Retrieving textures", but it now shows reimport progress of the lightmap.

A finally decided to actually test it with a debugger. Here's what I got:

On line 1088: texture_image->blit_rect(images[i * slices_per_texture + j], Rect2i(0, 0, slice_width, slice_height), Point2i(0, slice_height * j));

images is an array with one member in my case BUT is multiplied and added with other things which resulted in a bogus index of 1.

> images[0]
{reference=0x000001baca91e2b0 {format=FORMAT_RGBH (14) data={[size]=6144 [0]=167 'ง' [1]=48 '0' ...} ...} }
> images[1]
Array index out of bounds.

> i * slices_per_texture + j
1

[AThousandShips]

Needs further evaluation, ensure that the code is correctly transferred and correct

[atirut-w]

New version works now. Turns out I applied it wrong by also commenting out textures.resize(texture_count);.

Resolved

[clayjohn]

Makes sense to me. Kobewi confirmed in chat that it looks fine as well. I'm comfortable going ahead with this

[akien-mga]

Thanks!